If you mean collision attacks, this shouldn't be a problem with Git, since it uses Hardened SHA-1. Eventually, when Git fully migrates to SHA-2, we will offer that option as well.
> Is Hardened SHA-1 vulnerable?
> No, SHA-1 hardened with counter-cryptanalysis (see ‘how do I detect the attack’) will detect cryptanalytic collision attacks. In that case it adjusts the SHA-1 computation to result in a safe hash. This means that it will compute the regular SHA-1 hash for files without a collision attack, but produce a special hash for files with a collision attack, where both files will have a different unpredictable hash.
From https://shattered.io/
